Composite packaging material and process of manufacture thereof



Nov. 28, 1961 J. J. EBERL COMPOSITE PACKAGING MATERIAL AND PROCESS OF' MANUFACTURE THEREOF Filed April 4, 1958 INVENTOR.

Arran/fx United States Patent 3,010,860 `COMPOSIIII PACKAGING MATERIAL AND PROCESS 0F MANUFACTURE THEREOF James '.l. Eherl, Moylan, Pa., assignor to Scott Paper Company, Philadelphia, Pa., a corporation of Penn- Sylvania Filed Apr. 4, 1958, Ser. No. 726,467 11 Claims. (Cl. 154-50) IThe present invention relates to protective packaging material generally and more particularly to a composite wrapping material suitable for household and/or cornmercial packaging 'of foods and the like. This application constitutes a continuation in part of my earlier application, Serial No. 417,078, as iiled in the U.S. Patent Oice on March 18, 1954, now abandoned.

Wrapping materials and especially those which are used to protect foods, should possess certain essential characteristics such as strength, stability, crease resistance, etc., but of greater significance is the materials resistance to the passage of moisture and gases. Low moisture-vapor permeability insures -a reasonable maintenance of the original moisture content of the wrapped food and low gas permeability prevents loss of iiavor due to oxidation of the fats and result-ant production of aldehydes, ketones and short-chain fatty acids.

Wax paper has long been used as -a food wrapper-and has many desirable features such as low cost, and at least a moderately acceptable moisture-vapor permeability in the uncreased state. However, handling of the paper, and its subsequent creasing (as in wrapping food for storage) usually ruptures the wax film coating the paper and opens the material to the transmission of vapors therethrough. Other materials such as metal foil and polyethylene film are superior to Wax paper in some respects but are substantially more expensive than wax paper, particularly in such thicknesses as to be relatively impervious to vapors and to be self supporting, with the result that a substitution is not economically feasible.

Although prior art suggests materials in which the defects of common food wrappers are obviated or at least diminished, each has signican-t disadvantages. The present invention represents a new concept and provides a composite protective material wherein a discrete film of thermoplastic resinou'sl polymer which is compatible rresistant to mechanical deterioration.

Still another object of my invention is to provide heat sealable composite packaging material.

Another object of the present invention is to provide a process for uniting -a film of hydrocarbon wax with a sheet of synthetic film-forming polymeric material compatible with such hydrocarbon wax, while limiting the commingling of the yiilm substances to the zone immediately adjacent the interface of the films.

Further objects and advantages will be apparent by reference to the following description of cert-ain preferred embodiments thereof when taken in conjunction with the accompanying drawings, wherein:

4FIGURE 1 represents a schematic flow-diagram of one process for producing a composite sheet-material as contemplated by the present invention.

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FIGURE 2 represents a schematic view on a larger scale of -that portion of the process of FIGURE 1 wherein the synthetic film-forming material is applied to a waxed sheet.

FIGURE 3 represents a greatly enlarged cross-sectional view of a portion of one embodiment of sheet-materia-1 of the present invention.

FIGURES 4 and 5 represent additional embodiments of the inventive concept.

The present invention comprehends the broad principle of laminating two or more 0f lms' of compatible material to form a multi-ply sheet. It will be readily apparent from the following description that the composite material may be formed with or without a supporting base therefor.

By way of illustration, one embodiment of the sheet of the present invention represents an adptation of commercially avail-able wax paper, one type of which is produced by Scott Paper Company and sold under the trademark Cut-Rite. Such .a waxed paper 10 may consist of a base-sheet 11 of paper formed from chemical and/or semi-chemical pulps with a ream Weight of from ap' proxima-tely 16 to 25 pounds, carrying la iirmly adherent, substantially continuous coating of Wax on each surface.

The outer wax coatings indicated at 12 and 13 in FIG- URE 3 may be applied to the base-sheet 11 by procedures well known Ito the art. rPhe wax of the coating 12 and 13 may ybe a refined paraiiin wax having a melting point in the range of from approximately 130 F. to 145 F., a microcrystalline wax or any other miner-a1 Wax which is colorless, odorless, tasteless,'chemically inert and which is compatible with a special classof synthetic resins referred to herein-after.

Conversion of this waxed paper 10 into the packaging material of the present invention entails the application of a covering film of synthetic resin to at least one side thereof. The resin iilni application is effected upon a bonding apparatus 14 which includes an extruder 16, a cooling roll 17 and a pressure roll 18. In a preferred method, a'die 19 in communication with the extruder 16 is provided with an aperture 20 through which is discharged tilm yforming resin material 21 asa relatively thin sheet 22 of substantial width. The

sheet 22 flows continuously'from the die 19 and is drawn, with further attenuation into the nip between the pressure roll 18 and the cooling rol-1 17. The waxed paper 10 is also fed between the rolls`17 and 18 in a manner which permits the sheet 22 to contact one of the wax coatings 12 or 13. Preferably, the waxed paper is at room temperature whereas the sheet 22 is supplied at a temperature which is above the softening point of the resin as well as the melting point of the wax ilm.

As the heated sheet 22 comes into contact with the wax coating 12, the wax melts at the surface permittingv the wax and synthetic resin, under the thermally induced solvation action, to blend -at the interface 23 while the iilms are firmly cohered on passage through the nip ofL the rolls 17 and 18. As the composite assembly continues to advance'in contact with the cooling roll l7- (which is preferably maintained at a temperature of from 35 to 50 F.) the plastic materials set and vfurther migration of wax into the resin or commingling" between the resin and wax is halted. Manifestly, thel rapidity with which the composite sheet is cooled will affect the depth of the intermediate zone of the blended wax and resin that results -and in this manner a control f of the nature of the final product is enabled. It is only necessaryfor the relaization of optimum benefits from parent roll 24 for storage and subsequent rewinding into improved Amizes barrier' 3 smallerrolls, or it may be immediately cut and wound into s'rallV retail-size rolls.`Vr

Although it is preferred` to form the sheet 22 in an extruder closely adjacent the nip of the rolls 17 and 18,1it`is to be understood that the sheet 22 may be preformed ,and nrolled from a parent roll supportedV near the nip. In such event, the sheet 22, as it is fed from the parent roll, should 4be heated so as to be at a proper temperature vfor drawing to the desired thickness as it enters the Vnip of the rolls 17 and 18 and to admit of bonding to .one of the Vwax coatings 12er 13 lupon contact therewith;

Under actual conditions, the aperture 26 may be approximatcly12 mils wide and spaced from the nip a Sullicient'distance `to provide .a sheet 22 which, at its point of application to thewax paper, is approximately 0.25 miflfthckialthough it is to be understood that the sheet 22 may'v'ary'ih thickness from 0.1 -mil to 1.0 mil,rde pending uponthe protective properties demanded of the final y'product as well 'as the preferred cost thereof.

shas been indicated, the wax coatings 12 and i3 of the paper base 10 areformed of hydrocarbon waxes, including both the 'natural and synthesized waxes, with melting points inthe range of from l30rto 145 F. It is, of "course, possible to employV other paraiinic waxes whoseimeltingpoints Yare outside of this preferred range but'sp'ecial carermust be taken in such'cases to' prevent an' limprope'r blending of wax 'and 'resin in the final product. Y

It is also preferred that the resinous material forming the sheet 22 be polyethylene having a molecular weight in''exce'ss of16000 as this material readily vforms light gage films which exhibitfthe' necessary compatibility with hydrocarbon waxes. Other polyolefins, such as polyp'rol pylene and' polybutylene, which may be cast or extruded f v in lilmform, andr possessing'compatability with parainic v waxes' may be applied to the paper lo undercontrolled conditions'which result in' blending of the wax and resin pli'esatthe interface l23. Y

The nature ofthe waxed paper positeflproduot will 'alsoalfect the physical properties l0 entering the coml thereof. g Olstomarily, the waxed paper 10 may be char- Y arcteriredl as possessing a ream weight of 211/2 pounds ofiwhirc'h the base stock `11 comprises a paper'k having a ream weightof 171/2 pounds. Waxed papers with a rearn weight of' from 3G to 32 pounds including a base stock of a' paper having a ream weight of 25 pounds are avail-V able' and may be used in practicing the present invention."

The finished product is distinguished by its low mois:-V

ture-vaporjand gas permeability factors, as formedor whencreased and has the synthetic resin film adhered to the'w'ax :film through' the mediumv of a. commirigling Vof materials' at the interface between the films. The' packagingmaterial ofthe `present invention combines the con` tinuity"andjexibility of resin film with the strength and adaptability'tomechanical handling of supported Ywax films; @theicombined properties being superior to the additive'eectsu of both of theilms. 'I'he'strengt-h of the supportedA wax lmpermits usefofA thinner iilrns of synthetic' resin than wouldever be possible with self-sup` portedplastic films, and the tlm of synthetic resin, even creased;

In jafsecond embodiment of the invention, villustrated in FIGURE 4;^a"iilm 30 of ajsynthetic resin', a polyolein where being taken to arrcstmaterial migration before disruption of the films pense.

If it is desired, the advantages of my invention can be realized through a self-supporting composite of resin and wax films free of any supporting base medium. As shown in FIGURES, a iilm 36 of a synthetic resin such as polyethylene of a thickness of from 0.5 to 3`mils is covered with a lm 37 of refined parain wax after which the asl semblyV is heated to a temperature suflicient to accomplish the blending of the materials at their interface 38, While the major portion of the individual film integrity is retained. In heating the assembly it is not necessary lthat either component become completely iluidized to enable the interface blending since material compatability insures a'commingling thereof when only contiguous surfaces are rendered plastic orfsoftened.

The desirable Vgas permeability kcharacteristics of ,then several embodiments of my invention are illustrated by the following table which compares the gas permeability p constants of polyethylene film with ordinary wax paper and with a .composite resin-wax sheet-material. VThe gas permeability constants compared below are based upon the formula:

Unsupported Oreased Material Y and Creascd'. Creased Y `0f Present 0.25 mil Commercial Invention (0.25 Y Y Polyethylene Wax Paper lvlil Filmo i .nlm o-Polyethylene Varies from instantaneous. Varies from 4.08)(10-.9 to .OGlBXlO-g to 18.5Xl0-9. .00290)(109 A comparisonl of the moisture-vapor permeability measi urcments of the same materials also demonstrates theV exfinfthe'lghter gages; reinforces the wax iilrn and rniniruptures Whenthe composite material is Y ofthe typeheretofora'described, is applied and secured' to -af heavybase 21'of paper board. 'Y Conveniently, the

syntheticresin filmof any desired thickness varyingv from 0.2 tol miliseirtruded directlypup'on the paper board to Aivvhich it adheres strongly upon cooling.v A tilm Blof a hydrocarbon 'waxjis superposed'upon the vfilm 30hy i dip'waxin'g'orfroll coating as is conventional and the com- Y` posi'tel assembly subjected Vto heat .foraftime suicient to Y blending'fof the two films at their interface,` care ceptional Ycharacteristics of thef material ofv Ythe presentv inyention.' The moisture-vapor permeability comparisons y shown below are measured in grams of water vapor which Vpass` through a square meterA ofv material maintained at v 75 F. in an atmosphere of 60% "relative humidity Ii111 2.2i`

hours: I

I" Y Creased Mate' Unsupported Creased rial of Present arid Creased Commercial Invention 0.25 Mil Poly- Wax Paper Carrying a ethylene 0.25 Mil Film of Polyethylene K VVaries from Varies from i 0. 0 Y

It is believed, that VVfor Vmost purposes, the embodiment of my invention illustrated in FIGURE 3 of the drawing :be preferred,v The useof jpaper 'oflmoderate ream yweight as a support Yforuthe paran-wax layer to Awhich a f Yresin flrnY is adheredpermits vthe formation offa-iiexible wrapping material which is ideallysuit'edas' a freezer wrap,V aifordingV excellent protection for lany foodstuffs a encased therein. YWherefthe .multiplejspaced wax films are not necessary, one,- that is rthe Vone not adjacent the resin film, may be'eliminated to provide a cheaper lami;

f nate havinganoutside paper layer' Vavailable 'for printing.

The paper support for the wax film may be of increasing weight up to the paper board incorporated in the product shown in FIGURE 4. Faced corrugated paper board surfaced with the composite film of my invention will function with equal success in the formation of linerless folding cartons or interlining material for industrial packages. Metal foils, of which aluminum is typical, and films of non-fibrous materials, such as regenerated cellulose, may also be used to support the wax-resin composite film.

In those modifications wherein a wax overcoating forms the outside layer of the composite product, a heat seal operation on standard packaging machines is easily effected.

From the foregoing description of my inventive concept it will be obvious that Various changes, rearrangements and modifications in the component elements of the laminated packaging material are possible without departing from the scope of the invention as defined in the appended claims.

What I claim is:

l. A laminar protective packaging material composed of at least one film of a thermoplastic resinous polymer which is compatible with hydrocarbon wax and one film of hydrocarbon wax, said films being united only at their interface by a blending of the resin and wax.

2. A laminar protective packaging material composed of at least one lm of a thermoplastic resinous polymer which is compatible with hydrocarbon Wax and one film of hydrocarbon wax superposed thereon, said films being adhered substantially lcompletely only at their interface by a blending of the polymer and wax.

3. A laminar protective packaging material composed of at least one film of a polyolefin resin which is compatible with hydrocarbon Wax and one film of hydrocarbon wax, said films being adhered substantially completely only at their interface by a blending of the resin and the wax.

4. A laminar protective packaging material as defined in claim 3 in which the resin film is polyethylene and the wax film is a paraffin wax.

5. A laminar protective packaging material as defined in claim 3 in which the composite resin and wax films are supported upon a base.

6. A laminar protective packaging material as defined in claim 3 in which the composite resin and wax films are disposed upon and secured to -a base formed primarily of cellulose.

7. The method of forming a laminar protective packaging materia-l having low vapor permeability which comprises bringing together a film o-f a thermoplastic resinous polymer compatible with hydrocarbon Wax with a film of hydrocarbon Wax and subjecting the composite to-a temperature sufficient `to soften at least the surfaces of the films and to eect a blending only at the interface therebetween and subsequently cooling the composite to arrest material commingling and to maintain film continuity therein.

8. The process of coating base material with a hydrocarbon wax film and a film of a polyolefln resin compatible with hydrocarbon wax, said process comprising coating the base material with the wax film, heating the resin film -material sufficiently to soften at least the surfaces thereof and applying it to the wax film whereby to occasion a heat transfer and to induce material commingling only at the resin-wax film interface and substantially immediately thereafter chilling the composite to arrest material commingling and to retain lm continuity therein.

9. The process of coating base material with a hydrocarbon wax film and a film of polyethylene, said process comprising coating the base material with the wax film, heating the polyethylene film material to a temperature sufficient to soften at least the surfaces thereof and applying it to the wax film so as to initiate material blending at the interface between the films, and substantially immediately thereafter and without destroying the continuity of either film chilling each film to its solid state.

l0. The method of coating base material with a com. posite protective surfacing of low vapor permeability which comprises coating the base material with an adherent film of polyolefin resin which is compat-ible with hydrocarbon wax, superposing a film of hydrocarbon wax upon the resin film and subjecting the composite to a temperature sufficient to soften at least the contiguous surfaces of the films and to effect a blending only at the interface therebetween and subsequently restoring the films to the solid state Without interruption of film continuity.

11. A laminar protective packaging material comprising a' paper base and at least two films joined together and to one side of said base, one of which films is formed substantially entirely `of polyethylene and the other of which is formed substantially entirelyof hydrocarbon wax, the wax film intervening the base and the polyethylene film, said films being adhering substantially completely only at their interface by an immediate layer blending of the polyethylene and the waX.

References Cited in the file of this patent UNITED STATES PATENTS 2,369,450 Fischer Feb. 13, 1945 2,453,644 Steinkraus Nov. 9, 1948 2,572,959 Sparks et a-l. Oct. 30, 1951 2,582,037 Hyde Jan.V 8, 1952 2,607,712 Sturken Aug. 19, 1952 2,754,278 Wilson et al. July 10, 1956 2,828,237 Rosser Mar. 25, 1958 FOREIGN `rATl-:Nrs 641,568 Great Britain Aug. 16, 1950 

11. A LAMINAR PROTECTIVE PACKAGING MATERIAL COMPRISING A PAPER BASE AND AT LEAST TWO FILMS JOINED TOGETHER AND TO ONE SIDE OF SAID BASE, ONE OF WHICH FILMS IS FORMED SUBSTANTIALLY ENTIRELY OF POLYETHYLENE AND THE OTHER OF WHICH IS FORMED SUBSTANTIALLY ENTIRELY OF HYDROCARBON WAX, THE WAX FILM INTERVENING THE BASE AND THE POLYETHYLENE FILM, SAID FILMS BEING ADHERING SUBSTANTIALLY COMPLETELY ONLY AT THEIR INTERFACE BY AN IMMEDIATE LAYER BLENDING OF THE POLYETHYLENE AND THE WAX. 